A functional study of zinc–titanium coatings and exploration of the intrinsic correlation between angiogenesis and osteogenesis

With the development of implant applications, osseointegration has become a criterion for implant success. A good blood supply is essential for successful osseointegration. To improve the pro-angiogenic ability of the implants, in this experiment we introduced zinc into the titanium coating. The physical morphology, biocompatibility, pro-angiogenic ability, and osteogenic effect of the zinc-containing titanium coatings were investigated. The pro-angiogenic effect of zinc ions was determined, and the intrinsic link between angiogenesis and osteogenesis under the effect of zinc ions was investigated. Zinc-containing titanium coating was prepared using a micro-arc oxidation (MAO) technique. The physical properties of the coating materials were determined by analyzing the microstructure, roughness, hydrophilic properties, constituent elements, and ionic release of the coating. The biocompatibility of the coating materials was examined using apoptosis and proliferation assays of human umbilical vein endothelial cells (HUVECs). The pro-angiogenic function and osteogenic ability of the zinc-containing coating were investigated by CD31 immunofluorescence staining and quantitative polymerase chain reaction (q-PCR) assay. The optimal concentration of zinc ions for pro-angiogenesis was screened by ion assay. Conditioned media (CM) were prepared for the experiments. The intrinsic link between angiogenesis and osteogenesis was determined by q-PCR to detect the expression of genes related to HUVECs and BMSCs after culture in CM. The prepared Zn-containing micro-arc oxide coatings were shown to have good physical properties, stable Zn2+ release ability, and biocompatibility, as well as good angiogenic and osteogenic potential. In addition, ion experiments confirmed that 60 μM Zn2+ exhibited the best angiogenic effect; more importantly, a mutual promotion between angiogenesis and osteogenesis regeneration in the Zn2+ microenvironment was also found. The introduction of Zn2+ improved the implants' functionality and laid the foundation for the clinical application of Zn2+ pro-angiogenesis.